The present invention relates to cards such as magnetic cards and IC cards excellent in the balance among heat resistance, processability and embossability, a sheet suitable for such cards, and a thermoplastic resin composition for such cards and sheet.
In recent years, cards such as magnetic cards and IC cards are used for various applications. These cards are often embossed to three-dimensionally highlight symbols and characters. These cards are generally formed by a multi-layer sheet made of hard polyvinyl chloride resin. However, since polyvinyl chloride resin is poor in durability and heat resistance, it may be deformed when exposed to a high temperature, and an embossable card material excellent in heat resistance to substitute polyvinyl chloride resin has been being demanded.
Since 1,4-cyclohexanedimethanol derivative copolymerized polyesters are well embossable resins and are also excellent in mechanical strength and chemicals resistance, their application to cards is being examined. The 1,4-cyclohexanedimethanol derivative copolymerized polyesters are about 80.degree. C. in glass transition temperature and are characteristically excellent also in processability, since they can be thermally fused at low temperatures of about 110 to 120.degree. C. when processed into multi-layer sheets. However, because of the low glass transition temperature, they cannot be used for applications requiring heat resistance. One of methods conventionally considered for improving the heat resistance of 1,4-cyclohexanedimethanol derivative copolymerized polyesters is to blend a polymer with a high glass transition temperature.
Japanese Patent Laid-Open (Kokai) No. 53-94536 discloses a blend of a polycarbonate and poly(1,4-cyclohexanedimethanol terephthalate-co-isophthalate and a sheet made of it. The blend remains compatible in a wide range of mixing ratios, and has the transparency peculiar to the polycarbonate and poly(1,4-cyclohexanedimethanol terephthalate-co-isophthalate). The blend consisting of a polycarbonate and poly(1,4-cyclohexanedimethanol terephthalate-co-isophthalate) and a sheet made of it can be certainly improved in heat resistance by increasing the polycarbonate content. However, if heat resistance is improved, the processing temperature also rises, and the blend and sheet could not have both high heat resistance and high processability.
Japanese Patent Laid-Open (Kokai) No. 59-120648 discloses a blend consisting of a polycarbonate and a 1,4-cyclohexanedimethanol derivative copolymerized polyester. The blend can be substantially transparent (when 1,4-cyclohexanedimethanol content is larger), or translucent or opaque (when ethylene glycol content is larger), depending on which of 1,4-cyclohexanedimethanol or ethylene glycol is contained more in the glycol component of the 1,4-cyclohexanedimethanol derivative copolymerized polyester used. However, a substantially transparent blend is difficult to have both high heat resistance and high processability, since the processing temperature rises if the heat resistance is improved. Furthermore, said Japanese Patent Laid-Open (Kokai) 59-120648 does not state anything about the thermal fusibility of the sheet, and does not disclose anything about the applicability to a multi-layer sheet or cards.
Moreover, a blend consisting of a polycarbonate and a 1,4-cyclohexanedimethanol derivative copolymerized polyester has a problem that it is not suitable for embossable cards since if the polycarbonate content is increased, the embossability greatly declines though the heat resistance can be improved.
A polycarbonate alone is excellent in heat resistance, but is poor in embossability, and has been little examined for application to cards.
Japanese Patent Laid-Open (Kokai) No. 8-279150 discloses a card using non-oriented heat-crystallized polyethylene terephthalate. However, this card has a problem of low embossability though having excellent heat resistance.
The problem of the present invention is to provide cards such as magnetic cards and IC cards excellent in the balance among heat resistance, processability and embossability, a sheet suitable for such cards, and a thermoplastic resin composition suitable for such cards and sheet.